Ever tried flipping the car?  That's 5,000,000 kgs, and a LW flipper can toss it.  It's something to do with it being all one object; it's easier to move with hinges.  So, accurate flipping objects wouldn't really work.  They would consistently overrepresent your flipping power.
The Flip Test Dummy bot in the Scrappers team is a good measure for relative flipping power--it's easy to get under, and you can throw it high.